Statistical data with exact P values.

In this study, we investigated the role of PMCA4b in cell polarization and lumenogenesis. Our findings demonstrate that overexpression of PMCA4b in MCF-7 luminal epithelial-type breast cancer cells enhances cell polarization and promotes (pre-)lumen formation, thereby reinforcing epithelial characteristics. We further identified that the small GTPase Arf6 regulates the endocytic recycling of PMCA4b and is involved in the process of lumen formation. Additionally, RNAi-mediated silencing of the sole PMCA gene in <i>Drosophila melanogaster</i> disrupts lumen morphology in the salivary glands of <i>Drosophila</i> larvae, suggesting an evolutionarily conserved role for PMCA in lumenogenesis.